The use of catheter delivery systems for positioning and deploying therapeutic devices, such as dilation balloons, stents and embolic coils, in the vasculature of the human body has become a standard procedure for treating endovascular diseases. It has been found that such devices are particularly useful in treating areas where traditional operational procedures are impossible or pose a great risk to the patient, for example in the treatment of aneurysms in intracranial blood vessels. Due to the delicate tissue surrounding intracranial blood vessels, especially for example brain tissue, it is very difficult and often risky to perform surgical procedures to treat defects of intracranial blood vessels. Advancements in catheter deployment systems have provided an alternative treatment in such cases. Some of the advantages of catheter delivery systems are that they provide methods for treating blood vessels by an approach that has been found to reduce the risk of trauma to the surrounding tissue, and they also allow for treatment of blood vessels that in the past would have been considered inoperable.
Typically, these procedures involve inserting the distal end of a guiding catheter into the vasculature of a patient and traversing it through the vasculature to a predetermined delivery site. A vascular occlusion device, such as an embolic coil, is attached to the distal end of a deployment catheter which pushes the occlusion device through the guiding catheter and out of the distal end of the guiding catheter into the delivery site. Some of the problems that have been associated with these procedures relate to the accuracy of occlusion device placement. For example, once the occlusion device is pushed out of the distal end of the guiding catheter, the occlusion device cannot be retracted and may migrate to an undesired location. Often, retrieving and repositioning the occlusion devices requires a separate procedure and has the potential to expose the patient to additional risk.
In response to the above mentioned concerns, numerous devices and release mechanisms have been developed in an attempt to create delivery systems which provide both control of an occlusion device after the device has exited the guiding catheter and a rapid release or detachment mechanism to release the device from the deployment catheter once the occlusion device is in place.
One such device is disclosed in Lulo et al. U.S. Pat. No. 6,544,225, currently assigned to the same assignee as the subject application and hereby incorporated herein by reference. Lulo et al. discloses a hydraulic deployment system that has a deployment catheter having a lumen extending throughout the length of the catheter. The catheter has a distal end portion that is formed from a material which expands outwardly when a liquid is applied within the lumen of the catheter. A proximal end portion of an occlusion device is disposed in fluid-tight engagement within the lumen of the distal portion of the catheter. The proximal end portion of the occlusion device is typically a generally cylindrical section that, prior to assembly of the system, has a greater diameter than the distal end portion of the deployment catheter prior to assembly of the system and prior to expansion. A frictional engagement is formed by inserting the larger diameter proximal end portion of the occlusion device into the smaller diameter distal end portion of the deployment catheter. The objective of this prior system is to provide frictional engagement to not only form a fluid-tight seal but also to secure the occlusion device to the deployment catheter until the desired deployment of the occlusion device. When fluid is applied within the lumen of the deployment catheter, the distal end portion of the deployment catheter expands outwardly and the proximal end portion of the occlusion device is release, thereby deploying the occlusion device.
There remains a need for a coupling assembly that provides a high strength attachment between the occlusion device and the deployment catheter during the advancement of the occlusion device through the vasculature of a patient, and also allows for a rapid release of the occlusion device at the desired time of deployment, without having to rely upon tight sizing relationships between tubular members and tubular expansion.